|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 80
10
Recommenciations
SPACE TECHNIQUES
· An important part of general relativity remains completely
untested: the prediction of gravitomagnetic effects, though exceedingly
small in the solar system, should be checked experimentally.
The National Aeronautics and Space Administration's (NASA's) Relativity
Gyroscope Experiment (Gravity Probe B) is currently our best hope of
detecting such an effect the dragging of inertial frames by the rotating Earth.
The experiment calls for a level of technical sophistication not yet achieved in
a spaceborne instrument. We are pleased to note that NASA has initiated the
first phase of a two-stage program designed to accomplish this mission.
~ The highly successful use of solar-system ranging experiments to
test general relativity should be continued.
Ranging to planetary landers and orbiters has been particularly fruitful, and no
such opportunities should be missed. The Mars Observer mission appears to be
the first such opportunity if an accurate dual-frequency ranging system is
included. It also is of great importance to keep improving the solar-system
model with laser ranging to the Moon and radar ranging to the planets. These
techniques are extremely cost-effective means for increasing the stringency of
solar-system tests of general relativity.
· Two frontiers in gravitation research are the detection of gravita-
80
OCR for page 81
RECOMMENDA TIONS 81
tional radiation and the testing of general relativity in second order.
Promising ideas for space experiments in these areas should be
encouraged and studied.
Current concepts that warrant further study as possible future NASA missions
are a long-baseline (~106-km) laser interferometer in solar orbit to detect
gravitational waves in the important millihertz frequency range and a precision
optical interferometer (POINTS) capable of testing relativistic light deflection
by the Sun to second order. NASA currently has a proposal to send a precision
clock into a near-Sun orbit (STARPROBE) to measure the gravitational
redshift to second order, thus making a new (clock) measurement of the PEN
parameter if.
GROUND-BASED TECHNIQUES
· The strain amplitude sensitivity of interferometric gravitational-
wave detectors can be increased by 2 or more orders of magnitude by
the construction of baselines with lengths of ~5 km. This facility offers
the opportunity for a breakthrough in gravitational-wave detection and
should be pursued vigorously.
· Bar detectors are today the most sensitive gravitational-wave
detectors. A diverse research program should enjoy continued support,
with due attention being given to critical technologies. However,
systematic observations should play an increasing role as a guide in the
development of bar detectors.
· Pulsar observations have provided an impressive demonstration of
gravitational-wave damping in the binary pulsar and significant upper
limits for microhertz gravitational waves in the millisecond pulsar.
Searches for and observations of pulsars and other compact objects,
especially in binary systems, should be given high priority.
~ Laboratory experiments continue to play a role in gravitation
research by testing with increasing precision the basic principles and
predictions of gravitation theories. The fundamental nature of this
work more than justifies its small cost.
GRAVITATION THEORY
· Continued support for theoretical research is crucial to the health
of gravitation physics. The essential prerequisites for a strong theory
program are (a) support for a diversity of high-quality research areas,
(b) availability of means for communication among theorists and also
with scientists in other specialties, and (c) adequate opportunity for
entry into the field by talented young people.
OCR for page 82
82 GRA VI TA TION
· The strong relations of gravitation theory with other areas includ-
ing particle theory, gravitation experiment, astrophysics, and pure
mathematics are important to the field and should be fostered.
· Large-scale computation is playing an increasing role for certain
problems in gravitation theory, as in many other fields. We welcome
the initiatives currently under way to improve the access of physical
scientists to supercomputers and smaller computers.
Representative terms from entire chapter:
continued support
